JP7426805B2 - paper composition - Google Patents

Description

The present invention relates to a paper composition containing pulp recovered from an absorbent article and a water-absorbing resin, and a method for producing the same.

Conventionally, techniques for recycling used absorbent articles are known. For example, Patent Document 1 discloses a method for recycling used diapers in which the superabsorbent polymer contained in the disposable diapers can be turned into fine particles without using chemicals. The recycling method involves tearing up used disposable diapers, decomposing them into pulp components and non-pulp components, washing the mixture of the decomposed pulp components and non-pulp components such as vinyl with water, and then removing the waste from the mixture. The pulp components are separated and recovered, and the highly water-absorbent polymers mixed with the pulp components from which the non-pulp components have been removed and which have swollen upon absorption of water are processed into fine particles of 10 μm or less using a pulverizer without breaking the fibers of the pulp components. to form a suspension containing a particulate superabsorbent polymer, a pulp component, and water, and dehydrate the suspension to remove the superabsorbent polymer from the pulp component together with water. This is to recover pulp components.

Furthermore, Patent Document 2 discloses that used sanitary products are used by applying physical force to the used sanitary products in an aqueous solution containing polyvalent metal ions or an acidic aqueous solution with a pH of 2.5 or less. A step of decomposing the finished sanitary article into pulp fibers and other materials, a step of separating the pulp fibers from a mixture of pulp fibers and other materials generated in the decomposition step, and a step of separating the separated pulp fibers into a material with a pH of 2.5 or less. A method is described that includes a step of treating with an aqueous ozone-containing solution.

Further, Patent Document 3 discloses a method for recovering pulp fibers from used sanitary products containing pulp fibers and a superabsorbent polymer to produce recycled pulp that can be reused for sanitary products, and the method includes: The ozonation process includes an ozonation process in which the used sanitary goods or pulp fibers are immersed in an ozone-containing aqueous solution to decompose superabsorbent polymers in the used sanitary goods or attached to the pulp fibers. A method is described which is characterized in that simultaneously or after the ozonation step, the used sanitary products or pulp fibers are treated with a cationic antimicrobial agent.

Furthermore, Patent Document 4 describes a process of decomposing a polymeric water-absorbing material with ozonated water to reduce its molecular weight and solubilizing it, and a process of dissolving the polymeric water-absorbing material in ozonated water and discharging the polymeric water-absorbing material together with the ozonated water. include. The method for recovering pulp fibers of the present invention involves a step of decomposing the polymeric water-absorbing material with ozonated water to reduce its molecular weight and solubilizing it, and then dissolving the polymeric water-absorbing material in the ozonated water and discharging the polymeric water-absorbing material along with the ozonated water. A method of treating a polymeric water-absorbent material is described, which includes the steps of: removing pulp fibers from sanitary product residues;

Further, Patent Document 5 describes a method of decomposing a water-absorbing polymer using an acid or an alkali, or an acid or an alkali and an oxide.

Japanese Patent Application Publication No. 2010-59586 JP 2016-881 Publication JP2017-128840A JP 2017-100133 Publication Japanese Patent Application Publication No. 9-249711

In Patent Document 1, a superabsorbent polymer that has expanded upon absorption of water is broken into fine particles of 10 μm or less using a crusher without breaking the fibers of the pulp component, and the superabsorbent polymer and the pulp component are separated into fine particles. The pulp component is recovered by forming a suspension containing water and dehydrating the suspension to remove the superabsorbent polymer from the pulp component along with the water. In Patent Documents 2 to 4, the superabsorbent polymer adhering to the pulp fibers is removed by immersing the collected pulp fibers in an aqueous solution containing ozone. Therefore, the pulp fibers recovered by the methods of Patent Documents 1 to 4 do not contain superabsorbent polymers, have low adhesion between the pulp fibers, and have low viscosity.

By the way, pulp recovered from absorbent articles can be used, for example, to manufacture paper such as recycled paper. Conventionally, when manufacturing paper, a paper strength enhancer has been added in order to increase the adhesion between pulps contained in the manufactured paper and increase the strength of the paper. As mentioned above, the pulp fibers recovered by the methods of Patent Documents 1 to 4 have low adhesion between pulp fibers and low viscosity. Therefore, in order to produce recycled paper using the pulp fibers, conventional Therefore, it is necessary to add a paper strength agent.

Further, Patent Documents 1 and 5 do not particularly describe producing recycled paper using pulp recovered from used absorbent articles.
The present inventors have discovered that recycled paper with high strength can be obtained from a paper composition containing pulp and a water-absorbent resin recovered from absorbent articles, and have arrived at the present invention.

An object of the present invention is to provide a paper composition that can overcome the drawbacks of the prior art described above.

The present invention achieves the above object by providing a paper composition comprising pulp recovered from an absorbent article and a water-absorbing resin, wherein the water-absorbing resin has a low molecular weight. This has been achieved.
The present invention is a paper composition containing pulp recovered from an absorbent article and a water-absorbing resin, wherein the water-absorbing resin has an aperture of 500 μm in a wet state with 200 times the amount of water added by mass ratio. The above object has been achieved by providing a paper composition that passes through a sieve.

The present invention achieves the above object by providing recycled paper containing pulp recovered from absorbent articles and a water-absorbing resin, in which the water-absorbing resin has a lower molecular weight. be.

The present invention has achieved the above object by providing an absorbent article containing one or more selected from the group consisting of the above-mentioned paper composition and the above-mentioned recycled paper.

The present invention provides a method for producing a paper composition containing pulp and a water absorbent resin recovered from an absorbent article, comprising: a freezing step of freezing water in the absorbent article; a crushing step of crushing the absorbent article by applying an impact to the absorbent article; a separating step of separating the absorbent material containing the pulp and the water-absorbing resin from the sheet pieces derived from the absorbent article after the crushing step; The above object has been achieved by providing a method for producing a paper composition, which comprises, after the separation step, a low-molecularization step of reducing the molecular weight of the water-absorbing resin contained in the absorbent material. be.

The present invention provides a method for reducing the molecular weight of a water-absorbing resin, comprising: a water-impregnating step of adding water to the water-absorbing resin; a resin freezing step of freezing the water-absorbing resin after the water-impregnating step; and a freezing step. The above object has been achieved by providing a method for reducing the molecular weight of a water-absorbing resin, which includes a resin pulverizing step of subsequently pulverizing the water-absorbing resin.

The present invention is an apparatus for processing a water-absorbing resin into a low-molecular-weight solution, which includes a water-containing part that adds water to the water-absorbing resin, a resin freezing part that freezes the water-absorbing resin, and a part that crushes the water-absorbing resin. The above object has been achieved by providing a water-absorbing resin low-molecular treatment device that includes a resin crushing section.

According to the paper composition and the method for producing the same of the present invention, it is possible to provide a paper composition with high viscosity.
Moreover, according to the recycled paper of the present invention, recycled paper with high strength and no defects can be provided.
Furthermore, according to the method for reducing the molecular weight of a water-absorbing resin of the present invention, the water-absorbing resin can be efficiently reduced to a lower molecular weight.

FIG. 1 is a perspective view showing an example of an absorbent article used in the method for producing a paper composition of the present invention. FIGS. 2(a) to 2(e) are conceptual diagrams showing one embodiment of the method for producing a paper composition of the present invention.

The paper composition and recycled paper of the present invention contain pulp recovered from absorbent articles and water absorbent resin recovered from absorbent articles. The water absorbent resin in the present invention is recovered from absorbent articles and has a low molecular weight. That is, the molecular weight is lower than that in the state contained in the absorbent article.

The paper composition of the present invention is a powder mixture used as a raw material for paper, and is either in a dry state or in a liquid state mixed with a liquid such as water. The liquid state also includes a slurry state. The recycled paper of the present invention is paper containing pulp recovered from absorbent articles and water absorbent resin recovered from absorbent articles.

The paper composition of the present invention can be produced, for example, as follows. First, an absorbent article is frozen and then crushed to obtain a crushed absorbent article. Next, pulp and an absorbent material containing the water-absorbing resin are separated from the crushed material. Then, by lowering the water absorbent resin contained in the separated absorbent material, a paper composition containing pulp and the lower molecular weight water absorbent resin is produced.

The paper composition of the present invention has a higher viscosity in a slurry state than when it contains a water-absorbing resin that has not been reduced to a low-molecular weight, because it contains a water-absorbing resin that has not been reduced to a low-molecular weight.
To determine whether a water-absorbent resin is a low-molecular-weight water-absorbent resin, if the absorbent article or the water-absorbent resin contained therein is available, compare the molecular weight of the water-absorbent resin with the molecular weight of the water-absorbent resin to be determined. If the molecular weight of the water-absorbing resin to be determined is smaller, it can be determined that the water-absorbing resin to be determined has a lower molecular weight. The molecular weight of the water-absorbing resin can be measured, for example, by diffusivity using liquid chromatography or gel permeation chromatography, Rayleigh scattering of light, sedimentation time, viscosity, relative mass of molecules using a mass spectrometer, etc. However, since the water-absorbing resin has a crosslinked structure and an infinite network structure, it may be difficult to measure its molecular weight. Therefore, instead of comparing molecular weights, particle diameter, viscosity, sedimentation rate, or water absorption capacity are compared, and if the particle size, sedimentation rate, or water absorption capacity of the water-absorbing resin to be determined is smaller, or When the viscosity of the water-absorbing resin is higher, it can also be determined that the water-absorbing resin to be determined has a low molecular weight.

Regardless of whether the absorbent article or the water absorbent resin contained therein is available, the water absorbent resin contained in the absorbent article, paper composition, or recycled paper is a low molecular weight water absorbent resin. It may be determined whether or not there is one by using the following methods (1) to (6). Note that methods for determining whether or not the water-absorbing resin is contained in the paper composition or the recycled paper include, for example, NMR method (nuclear magnetic resonance), electron spin resonance method (ESR), FT-IR method, etc. (Fourier transform infrared spectroscopy), X-ray analysis, Raman spectroscopy, visible/ultraviolet spectroscopy (UV-VIS), visible light spectroscopy, ultraviolet-visible-near-infrared spectroscopy (UV-VIS-NIR) , millimeter wave imaging, terahertz imaging, cathodoluminescence (CL), fluorescence spectroscopy, methods using resin coloring reagents, thermogravimetric mass spectrometry (TG-MS), pyrolysis gas chromatography mass spectrometry (Py-GC/ MS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and the like.

(1) Judgment based on particle size If the particle size of the water-absorbent resin to be judged is significantly smaller than the particle size of general water-absorbent resins used in absorbent articles, it is determined that the water-absorbent resin has been reduced to a low molecular weight. Determined to be water absorbent resin.
Specifically, when the water-absorbing resin passes through a sieve with a mesh size of 500 μm in a wet state with 200 times the amount of water added in terms of mass ratio, the water-absorbing resin is determined to have a low molecular weight. Alternatively, if the water-absorbing resin has a particle size of 1 μm or less in a dry state, it is determined that the water-absorbing resin has a low molecular weight.

(2) Judgment based on viscosity If the viscosity of the water-absorbing resin to be judged after water absorption is significantly higher than that of general water-absorbing resins used in absorbent articles, low-molecular-weight It is judged to be a water-absorbing resin.
Specifically, if the water-absorbing resin has a viscosity of 150,000 mPa·s or more in a wet state with 20,000 times the amount of water added by mass, it is determined that the water-absorbing resin has a low molecular weight. The method for measuring viscosity will be described later in Examples.

(3) Judgment based on sedimentation speed of water-absorbent resin Compared to the sedimentation speed after water absorption of general water-absorbent resins used in absorbent articles, the sedimentation speed after water absorption of the water-absorbent resin to be judged is significantly If it is slow, it is determined that it is a low-molecular water-absorbing resin.
Specifically, if the settling time of the water absorbent resin measured by the settling time measuring method described below is 1 minute or more, preferably 10 minutes or more, and more preferably 1 hour or more, the water absorbent resin is It is determined that it is molecularized.
[Method of measuring settling time]
The absorbent resin is colored by absorbing pure water in an amount 20 times the mass ratio of the red dye added to the absorbent resin. Thereafter, the water-absorbing resin which has absorbed water and is colored is put into 20 times the amount of pure water or 0.05% CaCl ₂ aqueous solution and stirred. The depth of pure water or 0.05% CaCl ₂ aqueous solution is 5 cm. The time from the end of stirring until the colored water-absorbing resin precipitates is defined as the settling time. Whether or not the water-absorbing resin has precipitated is visually determined.

(4) Judgment based on water absorption capacity If the water absorption capacity of the water absorbent resin to be judged is lower than the water absorption capacity of general water absorbent resins used in absorbent articles, it is determined that the water absorption capacity has been reduced to a low molecular weight. It is determined to be resin.
Specifically, if the water absorption capacity of the water absorbent resin measured by the water absorption capacity measurement method described below is 10 times or less, preferably 5 times or less, the water absorbent resin is determined to have a low molecular weight. .
[Method of measuring water absorption capacity]
1 g of water-absorbing resin is placed in a cylinder with a diameter of 30 mm, and the bulk of the resin in a dry state is measured. Add 20 times the amount of pure water by mass, and measure the bulkiness in a wet state after 20 minutes. (Bulkiness in wet state)/(Bulkiness in dry state) is defined as water absorption capacity.

(5) Judgment based on sedimentation rate of paper composition or recycled paper Compared to the sedimentation rate of general paper compositions or recycled paper used for absorbent articles when disintegrated in water, the water-absorbing resin is If the water-absorbing resin contained in the paper composition or recycled paper to be determined has a significantly low sedimentation rate when disintegrated in water, the water-absorbing resin contained in the paper composition or recycled paper to be determined is low. It is determined to be a molecularized water-absorbing resin.
Specifically, the sedimentation time of a paper composition or recycled paper measured by the following method for measuring sedimentation time of a paper composition or recycled paper is 1 minute or more, preferably 10 minutes or more, and more preferably 1 hour. If the above is the case, it is determined that the water-absorbing resin contained in the paper composition or the recycled paper has a low molecular weight.
[Method for measuring settling time of paper composition or recycled paper]
The paper composition or recycled paper is colored by absorbing pure water in an amount 20 times the mass ratio of the red dye added to the paper composition or recycled paper. Thereafter, the water-absorbed and colored paper composition or recycled paper is poured into 20 times the amount of pure water or 0.05% CaCl ₂ aqueous solution, and stirred until loosened. The depth of pure water or 0.05% CaCl ₂ aqueous solution is 5 cm. The time from the end of stirring until the colored paper composition or recycled paper settles is defined as the settling time of the paper composition or recycled paper. Whether the paper composition or recycled paper has precipitated is visually determined.

The paper composition of the present invention will be explained by taking as an example paper composition 10, which is a preferred embodiment of the paper composition of the present invention.
As described above, the paper composition 10 contains the pulp and water absorbent resin recovered from the absorbent article. Absorbent articles are primarily used to absorb and retain body fluids excreted from the body, such as urine, menstrual blood, and vaginal discharge. The absorbent article may be unused or used. A used absorbent article refers to an absorbent article that has absorbed urine and other excreta excreted by the wearer, and contains moisture in the absorbent article, particularly in the absorbent core. Examples of excrement include body fluids excreted from the body, as well as feces and the like. Absorbent articles include, but are not limited to, disposable diapers, sanitary napkins, incontinence pads, panty liners, etc., and broadly include articles used to absorb fluids expelled from the human body. do. Absorbent articles typically include a liquid-permeable top sheet, a liquid-impermeable or water-repellent back sheet, and a liquid-retaining absorbent body interposed between the two sheets. The absorbent article may further include various members depending on its specific use. Such members are known to those skilled in the art. In the present invention, the absorbent article used for recovering pulp and water absorbent resin may be a single absorbent article, but preferably a plurality of absorbent articles. An absorbent article 1, which is an example of an absorbent article, is shown in FIG.

The absorbent article 1 is a used absorbent article. As the absorbent article 1, for example, a used absorbent article discarded by a nursing care facility, a childcare facility, or a household can be used. The absorbent article 1 includes an absorbent core 4 having an absorbent material, a top sheet 2, and a back sheet 3. The absorbent body 4 is interposed between the topsheet 2 and the backsheet 3, and the topsheet 2 and the backsheet 3 are joined at their peripheral edges with an adhesive or the like. Examples of the adhesive include hot-melt adhesives. The absorbent article 1 is a so-called deployable disposable diaper, and has a crotch area A at the center in the longitudinal direction, and a back crotch area that is one of the two areas extending from the front to the rear of the crotch area A. A fastening tape 5 is provided on both side edges of the side part B, and a fastening tape 5 is provided on the non-skin facing surface (the surface facing away from the wearer's skin side when worn) of the other region, the ventral part C. A landing zone 6 is provided for landing.
In the present invention, the absorbent article may be a so-called pants-type diaper. Pants-type diapers typically have a crotch section in the longitudinal center of the diaper, and both sides of the dorsal section, which is one of the two sections extending from the front and back of the crotch section. , the other part, both sides of the ventral part, are joined to each other to form a pair of side seal parts, a waist opening through which the wearer's torso passes, and a pair of legs through which the wearer's lower legs pass. An opening is formed.
Further, in the present invention, the absorbent article may be a so-called napkin, a pad, or a panty liner. A napkin typically has a crotch section at the center in its longitudinal direction, and is formed with a dorsal section extending forward and backward from the crotch section, and a ventral section that is the other section.

The top sheet 2, back sheet 3, absorbent core 4, and other constituent materials include those used in conventional absorbent articles. As the top sheet 2 and the back sheet 3, a nonwoven fabric, a sheet material, or the like made of synthetic resin such as thermoplastic resin is used. Examples of thermoplastic resins include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; one type of these resins may be used alone or two or more types may be used in combination. . As the absorbent body 4, an absorbent material wrapped in tissue paper or the like can be used.

The absorbent material forming the absorbent body 4 includes pulp and water absorbent resin. The pulp and water-absorbing resin include various pulps and water-absorbing resins conventionally used in absorbent articles, and there are no particular limitations.
As for the pulp, for example, the classification of origin includes wood pulp such as softwood (N wood) pulp and hardwood (L wood) pulp; cotton pulp, linter pulp, straw pulp, kenaf pulp, reed pulp, bagasse pulp, bamboo pulp, mulberry pulp, and fruit pulp. Non-wood pulp such as pulp; waste paper pulp, mechanical pulp such as ground wood pulp, refiner ground pulp, thermomechanical pulp, chemi-thermomechanical pulp; chemical pulp such as kraft pulp, sulfide pulp, alkaline pulp, etc. Can be mentioned.

The water-absorbing resin is preferably one that can absorb and retain liquid at least 20 times its own weight and can be gelled, such as a polymer or copolymer of starch, crosslinked carboxylmethylated cellulose, acrylic acid or an alkali metal salt of acrylic acid. etc., polyacrylic acid and its salts, and polyacrylate graft polymers. The shape of the water-absorbing polymer before being reduced in molecular weight may be spherical, lumpy, grape-like, powdered, film-like, or fibrous.

Moreover, the absorbent material may contain synthetic fibers and the like in addition to pulp and water-absorbing resin. The synthetic fibers may or may not be hydrophilized. Examples of synthetic fiber materials include polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET); polyamides such as nylon 6 and nylon 66; polyacrylic acid, polymethacrylic acid alkyl ester, Examples include polyvinyl chloride and polyvinylidene chloride, and one type thereof can be used alone or two or more types can be used in combination.

In the expandable absorbent article 1 shown in FIG. 1, the fastening tapes 5 are provided on both side edges of the back side portion B, respectively. The fastening tape 5 is fixed to side flap portions 11 located on both sides of the back side portion B in the width direction. The side flap portions 11 are portions extending outward in the diaper width direction from both side edges of the absorbent body 4, and are made of a laminate of a sheet for forming the three-dimensional gathers 7 and a back sheet 3.

The crushed material obtained by crushing the absorbent article 1 may include sheet pieces 8 derived from the absorbent article 1. Examples of the sheet piece 8 derived from the absorbent article 1 include the sheet piece 8 derived from the top sheet 2 or the back sheet 3. The sheet piece 8 may be a sheet piece produced by crushing the top sheet 2 or the back sheet 3, or may be the top sheet 2 or the back sheet 3 itself that maintains its original shape.

The paper composition 10 is a composition containing pulp and a water-absorbing resin, and can be used, for example, as a raw material for paper or recycled pulp. The paper composition 10 may be in the form of a slurry or may be in a dry state. In the paper composition 10, it is preferable that a water-absorbing resin is attached to the pulp.

The paper composition 10 has a high viscosity because the water-absorbing resin contained in the paper composition has a low molecular weight. Therefore, since the paper composition 10 has high adhesiveness between the pulps contained in the paper composition 10, the paper composition 10 can be prepared without adding a paper strength enhancer or without adding a paper strength enhancer to the paper composition 10. Even if the amount added is reduced, recycled paper with high strength can be produced.
In addition, the paper composition 10 has no grainy feel because the water-absorbing resin contained in the paper composition has a low molecular weight.

Further, the paper composition of the present invention is such that the water-absorbing resin contained in the paper composition passes through a sieve with an opening of 1000 μm in a wet state with 200 times the amount of water added by mass. It's okay. As a result, the paper composition of the present invention has a high viscosity. Therefore, in the paper composition of the present invention, since the adhesiveness between the pulps contained in the paper composition is high, it is possible to use the paper composition without adding a paper strength enhancer to the paper composition, or without adding a paper strength enhancer to the paper composition. Even if the amount of addition is reduced, recycled paper with high strength can be produced.
Furthermore, the paper composition of the present invention has no grainy feel.

A preferred structure of the paper composition 10 will be further explained.
From the viewpoint of increasing the viscosity of the paper composition 10, the water absorbent resin contained in the paper composition 10 is passed through a sieve with an opening of 1000 μm in a wet state with 200 times the amount of water added by mass ratio. It is preferable to pass through a sieve with an opening of 700 μm, more preferably to pass through a sieve with an opening of 500 μm.

Ash content refers to the amount of inorganic or non-flammable residue left after organic matter has been ashed. In order to enable its use as a sanitary material, the paper composition 10 has been prepared in accordance with the "Standards for Approval of Manufacturing and Sales of Sanitary Treatment Products" (Notice of the Pharmaceutical and Food Safety Bureau of the Ministry of Health, Labor and Welfare, No. 0325 No. 17 of the Pharmaceutical and Food Safety Bureau dated March 25, 2015). From the viewpoint of conforming to sanitary material standards for absorbent paper, etc., the ash content is preferably 0.65% by mass or less, more preferably 0.6% by mass or less, and the ash content It is more preferable that the content is 0.5% by mass or less. Further, the paper composition 10 preferably has a lower ash content, and there is no particular restriction on the lower limit, but it can be, for example, 0.001% by mass or more.

From the viewpoint of increasing the strength of paper, the paper composition 10 preferably contains a large amount of sodium polyacrylate derived from a water-absorbing resin, and the content of sodium in the ash is preferably 15% or more. It is more preferable that the content of sodium in the ash is 16% or more, and it is still more preferable that the content of sodium in the ash is 17% or more. In addition, from the viewpoint of reducing alkalization of paper, the paper composition 10 preferably has a sodium content of 100% or less in the ash, and more preferably has a sodium content of 75% or less in the ash. Preferably, the content of sodium in the ash is 50% or less.

The ash content can be measured, for example, as follows.
<Measurement method of ash content>
The ash content can be measured, for example, according to JIS Z 7302-4, or according to "5. Ash content test method" in "2. General test methods" of the Material Standard for Sanitary Treatment Products. That is, a sample was taken from a paper composition and/or recycled paper, the mass of the sample was accurately weighed, the sample was placed in a crucible, the mixture was ignited to ash until no char remained, and after being left to cool, it was ashed. The mass of the residue is precisely weighed, and the value obtained by dividing the mass of the incinerated residue by the mass of the input sample and multiplying it by 100 is defined as the ash content (mass %).

The content of sodium in ash can be measured, for example, as follows.
<Method for measuring sodium content in ash>
The sodium content in ash can be measured by using as a sample the material to be measured, such as a paper composition or recycled paper, which has been ashed, or the ash obtained when measuring the ash content. can. The sodium content can be measured by analyzing the composition of the sample. Examples of composition analysis include titration analysis, ion chromatography analysis, fluorescent X-ray analysis (EDX), spark emission spectrometry, spectrophotometry, inductively coupled plasma emission spectrometry, flame atomic absorption spectrometry, electrical heating atomic absorption spectrometry, Examples include inductively coupled plasma mass spectrometry.

Next, the recycled paper of the present invention will be explained.
The recycled paper of the present invention contains pulp and water absorbent resin recovered from absorbent articles, and the water absorbent resin has a low molecular weight. The recycled paper of the present invention can be produced, for example, using the paper composition 10 described above as a papermaking raw material. The recycled paper of the present invention is, for example, sanitary paper such as water-absorbent paper used for tissue paper, toilet paper, disposable diapers, sanitary products, etc., packaging paper such as kraft paper, cardboard paper, copy paper, inkjet paper, etc. Paper, information paper such as carbonless paper, photosensitive paper, and thermal paper, miscellaneous papers such as tracing paper, synthetic paper, insulating paper, and release paper, newspaper roll paper, uncoated printing paper, coated printing paper, and slightly coated paper. It may be printed paper, special printed paper, or the like.

The recycled paper of the present invention has high strength because it contains a low-molecular water-absorbing resin.
When the water-absorbing resin is not reduced in molecular weight, the water-absorbing resin may be in the form of particles that retain moisture inside. When the recycled paper contains grains made of a water-absorbing resin that has not been reduced to a low molecular weight as described above, the recycled paper has a grainy feel. Furthermore, if the recycled paper contains particles made of a water-absorbing resin that has not been reduced to a low molecular weight, as described above, the moisture inside the particles of the water-absorbing resin evaporates, and the water inside the particles of the water-absorbing resin evaporates. Hollowing may cause holes in the recycled paper.
The recycled paper of the present invention has no grainy feel because the water-absorbing resin contained in the recycled paper has a low molecular weight. Further, the recycled paper of the present invention is free from defects such as holes as described above.

In order to enable the recycled paper of the present invention to be used as a sanitary material, it is necessary to comply with the "Standards for Approval of Manufacturing and Sales of Sanitary Treatment Products" (Notice from the Director-General of the Pharmaceutical and Food Safety Bureau of the Ministry of Health, Labor and Welfare, No. 0325, No. 17 of the Pharmaceutical and Food Products Department, dated March 25, 2015). From the viewpoint of meeting the standards for sanitary materials such as absorbent paper, the ash content is preferably 0.65% by mass or less, more preferably 0.6% by mass or less, and the ash content is 0.5% by mass. It is more preferable that it is the following. Further, the lower the ash content is, the more preferable it is, and there is no particular restriction on the lower limit, but it can be, for example, 0.001% by mass or more.

From the viewpoint of increasing the strength of the paper, the recycled paper of the present invention preferably contains a large amount of sodium polyacrylate derived from a water-absorbing resin, and it is preferable that 15% or more of the ash content is sodium, and 16% of the ash content is preferably sodium. It is more preferable that the above is sodium, and it is still more preferable that 17% or more of the ash content is sodium. In addition, in the paper composition 10, from the viewpoint of reducing alkalization of paper and, for example, suppressing ink bleeding, it is preferable that 100% or less of the ash content is sodium, and it is preferable that 75% or less of the ash content is sodium. More preferably, 50% or less of the ash content is sodium.

Paper composition 10 and recycled paper using paper composition 10 can be suitably used for absorbent articles. Such absorbent articles have high strength and are made of hole-free recycled paper, so they can be used without tearing or breaking. In addition, in such an absorbent article, the water absorbent resin is easily fixed by the low-molecular absorbent resin contained in the recycled paper, making it possible to improve the absorbent performance. In addition, since such absorbent articles use recycled paper that does not have a grainy feel, they can be made to feel good on the skin and be gentle on babies' skin.

Next, a method for producing a paper composition of the present invention will be described based on a preferred embodiment thereof with reference to the drawings. FIG. 2 schematically shows a method for producing the above-described paper composition 10 as a first embodiment of the paper composition production method of the present invention.
The method for producing the paper composition 10 of the first embodiment shown in FIG. 2 includes a freezing step, a crushing step, a separation step, and a low-molecular-weighting step in this order. The low-molecular-weighting step included in the method for producing the paper composition 10 of the first embodiment is a preferred embodiment of the method for lowering the molecular weight of a water-absorbing resin of the present invention. In the method for producing the paper composition 10 of the first embodiment, an aggregate of a plurality of absorbent articles 1 is used as the absorbent article (see FIG. 2(a)). As described above, the absorbent article used in the method for producing the paper composition 10 of the first embodiment has various shapes such as an expanded type or a pants type, a state such as whether it is used or unused, and a size. It may be an aggregate of a plurality of absorbent articles having different sizes. That is, the manufacturing method of the first embodiment can be applied to a single type of absorbent article, but it can also be applied to a mixture of absorbent articles collected from nursing facilities or large-scale collection from households. It can also be applied to objects.

In the freezing step, the moisture in the absorbent article 1 is frozen (see FIG. 2(b)). The freezing process is performed to make it easier to crush the absorbent article 1, especially the absorbent core 4, in the subsequent crushing process. By freezing the moisture in the absorbent article 1 in the freezing step, it is possible to reduce the impact strength of the portion of the absorbent article 1 containing moisture, especially the absorber 4, compared to before freezing. When an impact is applied in the crushing step, the portions of the absorbent article 1 containing moisture, particularly the absorbent core 4, can be easily crushed. Since the absorbent article 1 has been used, the absorbent body 4 contains more water than the top sheet 2 and the back sheet 3. Therefore, when the moisture in the absorbent article 1 is frozen, the impact strength of the top sheet 2 and the back sheet 3 does not decrease much, but the impact strength of the absorbent body 4 decreases significantly. In the absorbent article 1 that has undergone the freezing process, the absorbent body 4 has a lower impact strength than the top sheet 2 and the back sheet 3, and is more likely to be crushed into smaller pieces.

The freezing step can be performed by placing the absorbent article 1 under low temperature conditions. Low-temperature conditions mean conditions that can freeze the moisture in the absorbent article 1. For example, the temperature is 0° C. or lower at 1 atmosphere. Since body fluids excreted from the body, such as urine absorbed by the absorbent article 1, contain salt, the freezing step is preferably carried out at -5°C from the viewpoint of reliably freezing the water in the absorbent article 1. Hereinafter, the temperature is more preferably -10°C or lower, and even more preferably -20°C or lower.

Even if the absorbent article 1 does not contain moisture, depending on the type of adhesive that joins the top sheet 2 and back sheet 3, the adhesive strength of the adhesive may be reduced by cooling during the freezing process. It may decrease. Examples of such adhesives include hot-melt adhesives that are used by heating and melting. Hot melt adhesives typically contain a base polymer, a tackifier, and a plasticizer. Specific examples of the base polymer include acrylic, silicone, rubber, and olefin polymers. Examples of the acrylic polymers include (co)polymers of vinyl monomers (ethylene-vinyl acetate copolymers, An example is a combination of merging, etc.). Examples of the silicone-based polymer include polydimethylsiloxane polymers. Examples of the rubber-based polymer include natural rubber, polyisoprene, styrene-butadiene copolymer (SBR), styrene-isoprene-styrene block copolymer (SIS), and styrene-butadiene-styrene block copolymer (SBS). ), styrene-ethylene-butadiene-styrene block copolymer (SEBS), and styrene-ethylene-propylene-styrene block copolymer (SEPS). As the adhesive strength of the adhesive decreases, the top sheet 2 and the back sheet 3 become easier to separate when an impact is applied during the crushing process, and the bonded portion of both sheets 2 and 3 peels off, causing both sheets 2 , 3, the absorbent body 4 can easily be taken out from between.

In the crushing step, an impact is applied to the absorbent article 1 to crush the absorbent article 1 (see FIG. 2(c)). The crushing step is performed to crush the absorbent article 1 and obtain a crushed mixture containing the constituent materials of the absorbent article 1 and small pieces thereof. The crushed mixture includes sheet pieces 8 originating from the topsheet 2 or backsheet 3, lumps 9 of absorbent material originating from the absorbent body 4, and the like. In the first embodiment, the mass 9 of absorbent material originating from the absorbent body 4 contains excreta.

The crushing step can be performed using, for example, a so-called crusher, a pulverizer, or the like. Examples of the crusher and crusher include compression type crushers, impact type crushers, grinding type crushers, shear type crushers, and devices that combine these. A compression type crusher is a device that crushes an object by compressing it, and includes, for example, a jaw crusher, a gyratory crusher, a cone crusher, a roll crusher, and the like. An impact crusher is a device that crushes an object by impacting the object with a hammer, _impact plate, etc., and crushes the object by impacting the object. Examples include impact crushers, hammer crushers, chain crushers, hammer mills, stamp mills, Examples include pin mills. A grinding type crusher is a device that crushes an object by grinding it, and includes, for example, a ball mill, a rod mill, a roller mill, a ring mill, an autogenous crusher, a jet mill, a rotary mill, a vibration mill, a planetary mill, and an attritor. , bead mill, etc. A shear type crusher is a device that crushes an object by shearing it, and includes, for example, a cutter mill, a single-shaft crusher, a twin-shaft crusher, and the like.

In the absorbent article 1 that has undergone the freezing process, the absorbent body 4 in particular is easily broken, so in the crushing process, the absorbent body 4 is crushed into smaller pieces than the top sheet 2 and the back sheet 3. Ru. Therefore, the lumps 9 of the absorbent material produced by crushing the absorbent body 4 are smaller than the sheet pieces 8 produced by crushing the topsheet 2 or the backsheet 3.
The sheet pieces 8 derived from the top sheet 2 or the back sheet 3 obtained after the crushing process have a mesh size that cannot pass through a 2 mm sieve, which is the standard length of the pulp contained in the absorbent body. is preferable, and in order to improve the separation speed in the subsequent separation step, it is more preferable that the aperture is large enough to not pass through a 5 mm sieve, even more preferably the size is such that it cannot pass through a 10 mm sieve, and It is even more preferable that the size is such that it cannot pass through a 20 mm sieve.
The absorbent material lump 9 obtained after the crushing step is preferably large enough to pass through a sieve with an opening of 2 mm, more preferably large enough to pass through a sieve with an opening of 5 mm, and preferably 10 mm. It is more preferable to have a size that allows it to pass through a 20 mm sieve, and even more preferably a size that allows it to pass through a 20 mm sieve.

In the method for producing the paper composition 10 of the first embodiment, it is preferable to create a state in which the absorbent material can be taken out from between the top sheet 2 and the back sheet 3 in the crushing step. Usually, in the absorbent article 1, the absorbent core 4 is interposed between a top sheet 2 and a back sheet 3 whose peripheral edges are joined to each other. Therefore, even if an impact is applied to the absorbent article 1 and the absorbent body 4 is broken into small pieces, the top sheet 2 and the back sheet 3 will not be broken, and the bond between the top sheet 2 and the back sheet 3 will be maintained. If the space between the top sheet 2 and the back sheet 3 remains sealed, the absorbent material cannot be taken out from between the two sheets 2 and 3, and in the subsequent separation process, the space between the top sheet 2 and the back sheet 3 remains sealed. 3 and the absorbent material cannot be separated. Therefore, in the crushing process, the absorbent material is removed from between the top sheet 2 and the back sheet 3 by breaking the top sheet 2 or the back sheet 3, or by breaking the bond between the top sheet 2 and the back sheet 3. It is preferable to put it in a state where it can be taken out.

In the separation process, the sheet pieces 8 derived from the absorbent article 1 and the absorbent material containing pulp and water absorbent resin are separated from the crushed mixture obtained in the crushing process (see FIG. 2(d)). . The sheet piece 8 derived from the absorbent article 1 is, for example, the sheet piece 8 derived from the top sheet 2 or the back sheet 3. The separation process is performed in order to be able to collect the sheet piece 8 derived from the absorbent article 1 and the absorbent material separately. In the first embodiment, since the sheet piece 8 and the lump of absorbent material 9 are different in size, a method of separating them based on their size can be used as a method for separating the two. In a first embodiment, the shredded mixture is sieved to separate the sheet pieces 8 and the absorbent material. The opening size of the sieve can be appropriately selected depending on the size of the sheet pieces 8 and the absorbent material lumps 9 contained in the crushed mixture.

In the method for producing the paper composition 10 of the first embodiment, the sheet pieces 8 and the absorbent material derived from the absorbent article 1 separated in the separation step are collected. Here, collecting means, for example, storing the separated sheet pieces 8 and the absorbent material in containers at separate locations, or moving them to separate locations. Various known methods can be used to collect the sheet pieces 8 and the absorbent material. For example, the sheet piece 8 and the absorbent material may each be housed in a container. For example, in the separation step, a belt conveyor or the like is placed under the sieve, and after separating the sheet pieces 8 onto the sieve and the absorbent material onto the belt conveyor, the belt conveyor is driven, The absorbent material etc. collected on the belt conveyor may be moved to another location.

In the molecular weight reduction step, the water absorbent resin contained in the collected absorbent material 9 is reduced in molecular weight. The low-molecular-weighting step may be performed on the absorbent material 9, or after separating the pulp and water-absorbent resin contained in the absorbent material 9, it may be performed on the separated water-absorbent resin. . After separating the pulp and water-absorbent resin contained in the absorbent material 9, when performing a low-molecularization process on the separated water-absorbent resin, after performing the low-molecularization process, the low-molecular water absorbent The paper composition 10 can be manufactured by mixing the resin and the separated pulp.
The method of reducing the molecular weight of the water-absorbing resin is not particularly limited, and may be a chemical method or a physical method. Chemical methods include methods using acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, etc., and methods using alkalis such as sodium hydroxide, potassium hydroxide, ammonia, calcium hydroxide, etc. Examples of methods using oxidizing agents and radicals include methods using various percarbonates, various perborates, peracetic acid, hydrogen peroxide, hypochlorites, chlorites, ascorbic acid, ozone, etc. It will be done.

In the method for producing the paper composition 10 of the first embodiment, in the molecular weight reduction step, the water absorbent resin is reduced in molecular weight by a physical method. More specifically, the low molecular weight process according to the first embodiment includes a water-containing process, a resin freezing process, and a resin pulverizing process in this order.

In the hydration step, the water-absorbing resin is hydrated. The water-containing process is used to make it easier to freeze the water-absorbent resin in the subsequent resin freezing process, and in the subsequent resin pulverization process, the swelling of the water-absorbent resin causes the molecular chains to extend, resulting in lower molecular weight. This is done to make it easier. The method of impregnating the water-absorbing resin with water is not particularly limited, and examples thereof include soaking it in water or an aqueous solution, spraying it, and absorbing urine, menstrual blood, feces, drips, and the like.

In the resin freezing step, the water absorbent resin is frozen. The resin freezing process is performed to make it easier to crush the water absorbent resin in the subsequent resin crushing process. Resin freezing can be performed by placing the absorbent material 9 or the water absorbent resin separated from the absorbent material 9 under low temperature conditions. Low-temperature conditions mean conditions that can freeze water in the water-absorbing resin. For example, the temperature is 0° C. or lower at 1 atmosphere. From the viewpoint of reliably freezing the water in the water-absorbing resin, the freezing step is preferably carried out at -5°C or lower, more preferably at -10°C or lower, and even more preferably at -20°C or lower. The method of freezing the water-absorbing resin is not particularly limited, and examples include methods of immersing the water-absorbing resin in a liquid refrigerant, a method of bringing it into contact with a solid refrigerant, a method of blowing cold air, and a method that combines these methods. Examples of the method of immersing the material in a liquid refrigerant include a method of immersing it in a liquid refrigerant, for example, brine (salt solution, alcohol, etc.), liquefied gas (liquid nitrogen, liquid carbon dioxide, etc.) and freezing it. Examples of the method of contacting the solid refrigerant include a method of cooling a metal plate from the inside or outside with a cooling substance and freezing the metal plate. Examples of the method of blowing cold air include a method of blowing cooled air to freeze the object, and a method of blowing liquefied gas boiled at an ultra-low temperature to freeze the object.

In the resin crushing step, the water absorbent resin is crushed. The resin crushing step is performed to reduce the molecular weight of the water absorbent resin. The resin crushing process can be performed using a crusher or a crusher similar to the crushing process described above. Moreover, the resin crushing process can be performed using a crusher, a crusher, etc. similar to the crushing process described above.

According to the method for producing the paper composition 10 of the first embodiment, the paper composition 10 is obtained as described above.
In the method for producing the paper composition 10 of the first embodiment, by performing the freezing step, the impact strength of the absorber 4 is reduced more than the impact strength of the sheet piece 8 derived from the absorbent article 1. Therefore, in the crushing step, when an impact is applied to the absorbent article 1, the absorbent core 4 is crushed into pieces smaller than the sheet pieces 8 derived from the absorbent article 1. The lump of absorbent material derived from the absorbent body 4 obtained after the crushing step and the sheet piece 8 derived from the absorbent article 1 are significantly different in size, so that the sheet piece 8 derived from the absorbent article 1 and The absorbent material can be separated from the absorbent material by a simple method such as passing through a sieve.
In addition, in the method for producing the paper composition 10 of the first embodiment, by freezing the moisture in the absorbent body 4, when the absorbent article 1 is crushed in the crushing step, the absorbent material 9 absorbs It becomes difficult to adhere to the sheet piece 8 derived from the sexual article 1. This makes it possible to prevent the sheet piece 8 derived from the absorbent article 1 and the absorbent material 9 from becoming difficult to separate in the separation process.
As described above, according to the method for producing the paper composition 10 of the first embodiment, the absorbent material 9 can be efficiently recovered from the absorbent article 1, and the efficiently recovered absorbent material can be Since the molecular weight reduction step can be performed, the paper composition 10 can be efficiently manufactured.
Furthermore, in the method for producing the paper composition 10 of the first embodiment, since the water-absorbing resin is reduced in molecular weight in the low-molecularization step, it is possible to produce a paper composition 10 with high viscosity.

According to the manufacturing method of the first embodiment, it is also possible to manufacture the paper composition 10 having a desired viscosity. In order to manufacture the paper composition 10 having a desired viscosity, for example, the degree of reduction in molecular weight of the water-absorbing resin may be adjusted in the reduction step. More specifically, the conditions for performing the low-molecular-weighting step may be adjusted, such as the resin water content in the water-containing step, the temperature in the resin freezing step, the processing time in the resin pulverization step, and the crushing strength in the resin pulverization step.

Further, by adjusting the amount of water-absorbing resin contained in the paper composition 10, the viscosity of the paper composition 10 can be adjusted to a desired viscosity. In order to adjust the amount of water absorbent resin contained in the paper composition 10, for example, after separating the pulp and water absorbent resin contained in the absorbent material 9 collected in the separation step, The amount of the water-absorbing resin is adjusted when the water-absorbing resin after the low-molecular-ization step is mixed with the separated pulp to produce the paper composition 10. do it. Moreover, the viscosity of the paper composition 10 can also be made into a desired viscosity by setting the ratio of the water-absorbing resin to the pulp in the paper composition 10 to a desired ratio.

The low-molecular-weighting process according to the first embodiment includes a water-containing process, a resin freezing process, and a resin pulverizing process in this order, so that the water-absorbing resin can be efficiently reduced in molecular weight.
In addition, in the low molecular weight process according to the first embodiment, the water absorbent resin is reduced in molecular weight by a physical method, so there is no need to perform a process of inactivating the water absorbent resin, and the number of processing steps can be reduced. Furthermore, since there is no need to use an inactivating agent containing a large amount of inorganic substances or chlorides, the ash and chlorine contents can be reduced.

Moreover, in the manufacturing method of the paper composition 10 of the first embodiment, it is preferable to have a rough crushing step before the freezing step. The coarse crushing process is a process of crushing the absorbent article 1 more coarsely than the crushing process. The rough crushing step is performed to roughly crush the absorbent article 1 to increase the surface area of the absorbent body 4 and to make the absorbent body 4 easier to freeze. It is preferable that the rough crushing process has a shorter processing time or a smaller impact on the absorbent article 1, or both, than the crushing process. In the rough crushing process, the absorbent article 1 can be crushed by applying an impact to the absorbent article 1, similarly to the crushing process. The type of impact may be the same or different in the rough crushing step and the crushing step.

In the rough crushing step, it is preferable to create a state in which the absorbent material and excrement can be taken out from between the top sheet 2 and the back sheet 3.
The sheet pieces derived from the top sheet 2 or the back sheet 3 obtained after the rough crushing step are preferably of a size that cannot pass through a sieve with an opening of 5 mm, and are not large enough to pass through a sieve with an opening of 10 mm. It is preferable that the size is large enough to pass through a sieve with an opening of 20 mm.
The mass of absorbent material obtained after the coarse crushing step is preferably large enough to pass through a sieve with a 5 mm opening, and preferably large enough to pass through a sieve with a 10 mm opening. It is more preferable that the size is such that it can pass through a 20 mm sieve.

By performing the rough crushing process before the freezing process, the surface area of the absorbent body 4 can be increased, and the water in the absorbent body 4 can be easily frozen in the freezing process. Further, by coarsely crushing the absorbent article 1 in advance in the rough crushing process, the time required for the crushing process can be shortened.

In addition, in the method for producing the paper composition 10 of the first embodiment, the moisture in the absorbent article 1 can be maintained in a frozen state during the steps after the freezing step, that is, one or both of the crushing step and the separation step. Preferably, it is carried out at temperature. As a result, in the process after the freezing process, the absorbent material adheres to the top sheet 2, back sheet 3, etc. through moisture, and in the separation process, the sheet pieces originating from the top sheet 2 or back sheet 3 and the absorbent material are separated. It is possible to prevent it from becoming difficult to separate. It is more preferable to perform both the crushing step and the separation step at a temperature that allows the water in the absorbent article 1 to remain frozen. The temperature at which the water in the absorbent article 1 can maintain a frozen state is preferably 0°C or lower, more preferably -5°C or lower, still more preferably -10°C or lower, and more preferably at 1 atm. More preferably, the temperature is -20°C or lower.

Further, in the method for producing the paper composition 10 of the first embodiment, the separation step is preferably performed while applying vibration to the crushed mixture obtained in the crushing step. Specifically, it is preferable to separate the sheet pieces originating from the topsheet 2 or the backsheet 3 and the absorbent material while applying vibrations. Thereby, even if the crushed mixture is in lumps, it can be separated while loosening the crushed mixture, so that the sheet pieces and the absorbent material can be accurately separated. Further, by applying vibration, a lump of absorbent material that is easily crushed due to freezing of water can be crushed into even smaller pieces. Therefore, the difference in size between the sheet piece and the lump of absorbent material can be made larger, so that the sheet piece and the absorbent material can be separated more easily.

Further, in the method for producing the paper composition 10 of the first embodiment, it is preferable that the step after the resin freezing step, that is, the resin pulverizing step, be performed at a temperature that allows the water-absorbing resin to maintain a frozen state. This makes it possible to carry out the resin crushing step while maintaining the water absorbent resin in a state where it is easy to crush. The temperature at which the water absorbent resin can maintain a frozen state is preferably 0°C or lower, more preferably -5°C or lower, still more preferably -10°C or lower, and even more preferably - The temperature is below 20°C.

Next, a second embodiment of the method for producing a paper composition of the present invention will be described. Regarding the second embodiment, only the points different from the first embodiment will be described. The second embodiment is the same as the first embodiment in that it is not particularly described, and the description of the first embodiment applies as appropriate.

The method for producing the paper composition 10 of the second embodiment includes a coarse crushing step, a freezing step, a separation step, and a low-molecular-weighting step in this order. The rough crushing step, the freezing step, the separation step, and the low-molecularization step can be performed in the same manner as the rough crushing step, freezing step, separation step, and low-molecularization step in the first embodiment.

In the method for producing the paper composition 10 of the second embodiment, first, a rough crushing step is performed, and the absorbent article 1 is roughly crushed. Next, a freezing step is performed to freeze the moisture in the absorbent article 1. Thereafter, a separation step is performed to separate and collect sheet pieces originating from the top sheet or the back sheet and the absorbent material. In the second embodiment, unlike the first embodiment, a crushing step is not performed after the freezing step.

In the method for producing the paper composition 10 of the second embodiment, the surface area of the absorbent body 4 is increased by the rough crushing step, and the water in the absorbent body 4 is easily frozen. In addition, the freezing process freezes the moisture in the absorbent body 4, making it difficult for the absorbent material to adhere to the top sheet 2 and back sheet 3. Therefore, in the separation and recovery method of the second embodiment, as in the first embodiment, the sheet pieces originating from the top sheet 2 and the back sheet 3 and the absorbent material are separated by a simple method such as passing through a sieve. It can be separated and recovered by

In the method for producing the paper composition 10 of the second embodiment, it is preferable that the sheet piece and the absorbent material be separated while being vibrated in the separation step. As a result, the absorbent body 4 whose impact strength has decreased due to freezing of moisture can be crushed into smaller pieces, so that the size of the sheet pieces and the lump of absorbent material originating from the absorbent body 4 can be reduced. It becomes possible to make a larger difference between the sheets, and the sheet piece and the absorbent material can be separated and collected more easily.

Next, an embodiment of a paper composition manufacturing apparatus suitably used in the method for manufacturing the paper composition 10 of the first embodiment of the present invention will be described. The paper composition manufacturing apparatus of this embodiment is a manufacturing apparatus that can manufacture the paper composition 10 described above. The apparatus for producing the paper composition 10 of this embodiment includes a freezing section, a crushing section, a separating section, and a low molecular weight section in this order from upstream to downstream of the apparatus. The low-molecular-weighting unit included in the apparatus for producing the paper composition 10 of this embodiment is a preferred embodiment of the water-absorbing resin low-molecularization apparatus of the present invention. Moreover, it is preferable that the manufacturing apparatus of the paper composition 10 of this embodiment has a coarse crushing part which roughly crushes the absorbent article 1 upstream of the freezing part. Moreover, in the manufacturing apparatus of this embodiment, each part may be independent from each other, or may be connected and continuous by a conveying part consisting of a belt conveyor or the like.

The freezing section is configured to be able to freeze the moisture in the absorbent article 1. Specifically, it is preferable that the freezing unit includes a freezing device that can perform the freezing process described above. Examples of freezing devices include devices that immerse the material in liquid refrigerant, devices that bring it into contact with solid refrigerant, devices that blow cold air, and devices that combine these. Examples of devices for immersing in a liquid refrigerant include a brine refrigerator that freezes the object by immersing it in a liquid refrigerant, such as brine (salt solution, alcohol, etc.) or liquefied gas (liquid nitrogen, liquid carbon dioxide, etc.). Examples of devices that bring the material into contact with a solid refrigerant include a contact refrigerator, which cools a metal plate from the inside or outside with a cooling substance, and freezes the solid refrigerant by sandwiching the metal plate between the metal plates. Examples of devices that blow cold air include air blast refrigerators that freeze with chilled air, and liquefied gas refrigerators that spray and freeze liquefied gas boiled at extremely low temperatures.

The crushing section is configured to apply an impact to the absorbent article 1 and crush the absorbent article 1. Specifically, it is preferable that the crushing section includes a crushing device capable of performing the above-described crushing process. As a crushing device, for example, a so-called crusher, a pulverizer, or the like can be used. Examples of the crusher and crusher include compression type crushers, impact type crushers, grinding type crushers, shear type crushers, and devices that combine these. A compression type crusher is a device that crushes an object by compressing it, and includes, for example, a jaw crusher, a gyratory crusher, a cone crusher, a roll crusher, and the like. An impact crusher is a device that crushes an object by impacting it with a hammer, impact plate, etc., and crushes the object by impacting the object, such as impact crushers, hammer crushers, chain crushers, hammer mills, stamp mills, and pin mills. etc. A grinding type crusher is a device that crushes an object by grinding it, and includes, for example, a ball mill, a rod mill, a roller mill, a ring mill, an autogenous crusher, a jet mill, a rotary mill, a vibration mill, a planetary mill, and an attritor. , bead mill, etc. A shear type crusher is a device that crushes an object by shearing it, and includes, for example, a cutter mill, a single-shaft crusher, a twin-shaft crusher, and the like.

The separation section is configured to be able to separate the sheet piece 8 originating from the absorbent article 1 and the absorbent material 9. Specifically, it is preferable that the separation unit includes a separation device that can perform the separation process described above. Examples of separation devices include devices that use screens or filters, devices that use airflow, devices that use gravity, devices that use vibration, devices that use rollers, and devices that combine these. . A device using a screen or filter is a device that separates substances depending on the size of the mesh of the screen or filter, and includes, for example, a sieve, a filter, and a screen. Devices that use airflow are devices that separate fluids such as air and liquid according to their specific gravity and shape, such as mesh separators, swirling sieves, cage separators, screw press collectors, air separators, screw press separators, dust collectors, etc. Examples include jet separators. Devices that use gravity are devices that separate using falling speed and sedimentation depending on specific gravity and shape, such as water specific gravity separation, heavy liquid separation, liquid nitrogen specific gravity separation, liquefied carbon dioxide specific gravity separation, air drop separation, etc. can be mentioned. Devices using vibration are devices that promote separation by vibration, and include, for example, a vibrating sieve, a gyro sifter, a circular vibrating sieve, a Eurus screen, and a ballistic separator. A device using rollers is a device that separates particles by a difference in gap due to a difference in roller size, and includes, for example, a particle size sorter. Examples of the combined separation device include a vario separator that combines filter separation, airflow separation, and vibration separation.

Further, it is preferable that either or both of the crushing section and the separating section include cooling means. As the cooling means, one that can maintain the temperature of the crushing section or the separating section at a temperature at which the moisture in the absorbent article 1 can be maintained in a frozen state can be used. Examples of such cooling means include, for example, a method in which the crushed portion is separated or separated while immersed in a liquid refrigerant, a method in which the crushed portion is separated or separated while in contact with a solid refrigerant, a method in which the crushed portion is separated or separated while being blown with cold air, and Examples include devices that can perform methods that combine these methods. A method of separating the crushing section while immersed in a liquid refrigerant is to maintain the frozen state by immersing the crushing section in a liquid refrigerant, such as brine (salt solution, alcohol, etc.) or liquefied gas (liquid nitrogen, liquid carbon dioxide, etc.). Alternatively, a method of separating may be mentioned. Examples of the method of contacting the solid refrigerant include cooling the metal plate of the crusher or separator with a cooling substance from the inside or outside, and maintaining the frozen state by separating or separating the crushing part with the metal plate. Methods of blowing cold air include blowing cooled air onto a crusher or separator, or supplying cooled air to a crusher or separator to maintain a frozen state, or blowing liquefied gas boiled at an ultra-low temperature into a crusher or separator. Alternatively, methods include spraying it onto a separator, or supplying liquefied gas boiled at an ultra-low temperature to a crusher or separator to maintain a frozen state.

The low-molecular-weighting section is configured to be able to reduce the molecular weight of the water-absorbing resin contained in the collected absorbent material 9. Specifically, it is preferable that the low-molecular-weighting section is equipped with a low-molecular-weighting device capable of performing the above-described low-molecular-weighting step. Examples of the low-molecularization device include, for example, a device equipped with a resin freezing section and a resin crushing section when performing physically, and a device equipped with a reaction tank as a reaction section when performing chemically. .

Furthermore, it is preferable that the low-molecular-weighting section includes a water-containing section, a resin freezing section, and a resin crushing section in this order from upstream to downstream of the paper composition 10 manufacturing apparatus of this embodiment.
The water-containing portion is configured to allow the water-absorbing resin to contain water. Specifically, it is preferable that the water-containing section includes a water-containing device capable of performing the water-containing step described above. Examples of water-containing devices include immersion baths, spray devices, showers, water curtains, and the like.

The resin freezing section is configured to be able to freeze the water absorbent resin. Specifically, the resin freezing section is preferably equipped with a resin freezing device capable of performing the resin freezing process described above. Examples of the resin freezing device include the freezing device described above.

The resin crushing section is configured to crush the water absorbent resin. Specifically, the resin crushing section is preferably equipped with a resin crushing device capable of performing the resin crushing process described above. Examples of the resin crushing device include the crushing device described above.

Moreover, it is preferable that the resin pulverization has a cooling means. As the cooling means, one that can maintain the temperature of the resin crushing section at a temperature at which the water-absorbing resin can be maintained in a frozen state can be used. As such a cooling means, a cooling means that can be used as a cooling means included in the above-mentioned crushing section or separating section can be mentioned.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments.
For example, in the manufacturing method of the first embodiment, a sieve was used in the separation step, but instead of this, an air stream is applied to the crushed mixture of the absorbent article 1 to separate small lumps of absorbent material. The sheet piece 8 derived from the absorbent article 1 and the absorbent material 9 may be separated by moving the sheet piece 8 to the location.

Further, when the absorbent article 1 contains excrement as in the method for producing the paper composition 10 of the first and second embodiments, in the separation step, the sheet pieces 8 derived from the absorbent article 1 and , the absorbent material 9 and the excrement are preferably separated. This makes it possible to separate and collect the sheet piece that does not contain excrement, the absorbent material, and the excrement. When separating the sheet piece from the absorbent material and excrement, the sheet piece may be separated into a mixture of the absorbent material and excrement, or the sheet piece, the absorbent material and the excrement may be separated into three parts: the sheet piece, the absorbent material and the excrement. It may be separated into

The present invention further discloses the following additional notes.
<1>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
A paper composition in which the water-absorbing resin has a low molecular weight.
<2>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
The water-absorbing resin is a paper composition that passes through a sieve with an opening of 500 μm in a wet state with 200 times the amount of water added by mass.
<3>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
The water-absorbing resin preferably passes through a sieve with an opening of 1000 μm, and more preferably through a sieve with an opening of 700 μm, in a wet state with 200 times the amount of water added by mass. A paper composition that preferably passes through a sieve with an opening of 500 μm.
<4>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
A paper composition, wherein the water-absorbing resin has a particle size of 1 μm or less in a dry state.

<5>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
The water-absorbing resin is a paper composition having a viscosity of 150,000 mPa·s or more in a wet state with water added in an amount of 20,000 times by mass.
<6>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
The water-absorbing resin is a paper composition having a settling time of 1 minute or more, preferably 10 minutes or more, and more preferably 1 hour or more.
<7>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
The water-absorbing resin has a water-absorbing capacity lower than that of general water-absorbing resins used in absorbent articles.

<8>
The paper composition according to any one of <1> to <7>, wherein 15% or more of the ash content is sodium.
<9>
Preferably, 15% or more of the ash content is sodium, more preferably 16% or more of the ash content is sodium, even more preferably 17% or more of the ash content is sodium, and 100% or less of the ash content is sodium. According to any one of the above <1> to <7>, preferably 75% or less of the ash content is sodium, and even more preferably 50% or less of the ash content is sodium. Composition for paper.
<10>
The paper composition according to any one of <1> to <9>, wherein the ash content is 0.65% by mass or less.
<11>
The ash content is preferably 0.65% by mass or less, more preferably 0.6% by mass or less, and even more preferably 0.5% by mass or less. Further, the lower the ash content is, the more preferable it is, and there is no particular restriction on the lower limit, but for example, it can be 0.001% by mass or more, for the paper according to any one of <1> to <9> above. Composition.

<12>
Recycled paper containing pulp and water absorbent resin recovered from absorbent articles,
Recycled paper in which the water-absorbing resin has a low molecular weight.
<13>
Recycled paper containing pulp and water absorbent resin recovered from absorbent articles,
The water-absorbing resin is recycled paper that passes through a sieve with an opening of 1000 μm in a wet state with 200 times the amount of water added by mass.
<14>
A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
The water-absorbing resin preferably passes through a sieve with an opening of 1000 μm, and more preferably through a sieve with an opening of 700 μm, in a wet state with 200 times the amount of water added by mass. The recycled paper is preferably one that passes through a sieve with an opening of 500 μm.

<15>
Recycled paper containing pulp and water absorbent resin recovered from absorbent articles,
The water-absorbing resin is recycled paper having a particle size of 1 μm or less in a dry state.
<16>
Recycled paper containing pulp and water absorbent resin recovered from absorbent articles,
The water-absorbing resin is recycled paper having a viscosity of 150,000 mPa·s or more in a wet state with 20,000 times the amount of water added by mass.
<17>
Recycled paper containing pulp and water absorbent resin recovered from absorbent articles,
The water-absorbing resin is a recycled paper whose settling time is 1 minute or more, preferably 10 minutes or more, and more preferably 1 hour or more.
<18>
Recycled paper containing pulp and water absorbent resin recovered from absorbent articles,
The water-absorbing resin is a recycled paper whose water-absorbing capacity is lower than that of general water-absorbing resins used in absorbent articles.

<19>
The recycled paper according to any one of <12> to <18>, wherein 15% or more of the ash content is sodium.
<20>
Preferably, 15% or more of the ash content is sodium, more preferably 16% or more of the ash content is sodium, even more preferably 17% or more of the ash content is sodium, and 100% or less of the ash content is sodium. According to any one of <12> to <18> above, it is preferable that 75% or less of the ash content is sodium, and even more preferably that 50% or less of the ash content is sodium. Recycled paper.
<21>
The recycled paper according to any one of <12> to <20>, wherein the ash content is 0.65% by mass or less.

<22>
The ash content is preferably 0.65% by mass or less, more preferably 0.6% by mass or less, and even more preferably 0.5% by mass or less. Further, the lower the ash content is, the more preferable it is, and there is no particular restriction on the lower limit, but for example, it can be 0.001% by mass or more, for the paper according to any one of <12> to <20> above. Composition.
<23>
1 selected from the group consisting of the paper composition according to any one of <1> to <11> above, and the recycled paper according to any one of <12> to <22> above. Absorbent articles containing one or more species.

<24>
A method for producing a paper composition comprising pulp recovered from an absorbent article and a water absorbent resin, the method comprising:
a freezing step of freezing the moisture in the absorbent article;
After the freezing step, a crushing step of applying an impact to the absorbent article to crush the absorbent article;
After the crushing step, a separation step of separating the absorbent material containing the pulp and the water-absorbing resin from the sheet piece derived from the absorbent article, and
A method for producing a paper composition, comprising, after the separation step, a low-molecularization step of reducing the molecular weight of the water-absorbing resin contained in the absorbent material.

<25>
The method for producing a paper composition according to <24>, further comprising a coarse crushing step of roughly crushing the absorbent article before the freezing step.
<26>
The method for producing a paper composition according to <24> or <25> above, wherein the crushing step is performed at a temperature that allows water in the absorbent article to remain frozen.
<27>
The method for producing a paper composition according to any one of <24> to <26>, wherein the separation step is performed at a temperature that allows water in the absorbent article to remain frozen.
<28>
The temperature at which the water in the absorbent article can maintain a frozen state is preferably 0° C. or lower, more preferably -5° C. or lower, and even more preferably -10° C. or lower at 1 atmosphere, The method for producing a paper composition according to <26> or <27>, which is even more preferably -20°C or lower.
<28>
In the separating step, the sheet piece originating from the top sheet or the back sheet and the absorbent material are separated while being vibrated, according to any one of <24> to <28>. A method for producing a paper composition.

<29>
The molecular weight reduction step is as follows:
a hydrating step of adding water to the water-absorbing resin;
a resin freezing step of freezing the water absorbent resin;
The method for producing a paper composition according to any one of <24> to <28>, comprising a resin pulverizing step of pulverizing the water-absorbing resin.
<30>
The method for producing a paper composition according to item <29> above, wherein the resin pulverization step is performed at a temperature that allows water in the absorbent resin to remain frozen.
<31>
The temperature at which water in the absorbent resin can maintain a frozen state is preferably 0°C or lower, more preferably -5°C or lower, still more preferably -10°C or lower, and more preferably at 1 atm. The method for producing a paper composition according to <30> above, which is more preferably -20°C or lower.
<32>
The method for producing a paper composition according to any one of <29> to <31>, wherein the freezing step is performed by placing the absorbent resin under low-temperature conditions.
<32>
For paper according to any one of <29> to <32>, the resin freezing step is preferably carried out at -5°C or lower, more preferably -10°C or lower, even more preferably -20°C or lower. Method for producing the composition.

<33>
A method of reducing the molecular weight of a water-absorbing resin,
a hydrating step of adding water to the water-absorbing resin;
a resin freezing step of freezing the water-absorbing resin after the hydration step;
A method for reducing the molecular weight of a water-absorbing resin, comprising, after the freezing step, a resin pulverizing step of pulverizing the water-absorbing resin.

<34>
The method for reducing the molecular weight of a water absorbent resin according to item <33> above, wherein the resin pulverization step is performed at a temperature that allows water in the absorbent resin to remain frozen.
<35>
The temperature at which water in the absorbent resin can maintain a frozen state is preferably 0°C or lower, more preferably -5°C or lower, still more preferably -10°C or lower, and more preferably at 1 atm. The method for reducing the molecular weight of a water-absorbing resin according to <34> above, which is more preferably -20°C or lower.
<36>
The method for reducing the molecular weight of a water absorbent resin according to any one of <33> to <35>, wherein the resin freezing step is performed by placing the absorbent resin under low temperature conditions.
<37>
The water absorption according to any one of <33> to <36>, wherein the resin freezing step is preferably carried out at -5°C or lower, more preferably -10°C or lower, even more preferably -20°C or lower. A method for reducing the molecular weight of resin.
<38>
An apparatus for processing water-absorbing resin to lower molecular weight,
a water-containing part that contains water in the water-absorbing resin;
a resin freezing section that freezes the water absorbent resin;
A water absorbent resin low molecular weight processing apparatus, comprising a resin crushing section that crushes the water absorbent resin.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the following Examples.

<Test 1>
Test 1 was conducted to evaluate whether it is possible to reduce the molecular weight of a water-absorbing resin by freezing the water-absorbing resin and then crushing the water-absorbing resin.
[Manufacture of resin-containing liquid]
(Example 1)
(1) First, 200 g of ion-exchanged water was absorbed into 1 g of water absorbent resin. As the water-absorbing resin, a polyacrylic acid sodium salt polymer (IM997, manufactured by Sundia Co., Ltd.) was used.
(2) Next, the water absorbent resin was placed in liquid nitrogen and frozen.
(3) Then, take out the water absorbent resin from the liquid nitrogen, put it into a crusher (manufactured by Osaka Chemical Co., Ltd., Wonder Crusher, model: WC-3, Navis product number: 1-3380-01), and use the rotation speed memory 3 to Grind for 1 minute.
(4) The frozen and pulverized product obtained in (3) was melted at room temperature to obtain a resin-containing liquid.
The resin-containing liquid thus obtained was used as the resin-containing liquid of Example 1. The resin-containing liquid of Example 1 was in the form of a slurry.

(Comparative example 1)
A resin-containing liquid of Comparative Example 1 was obtained in the same manner as in Example 1 except that step (2) in Example 1 was not performed.
(Comparative example 2)
200 g of a 5% CaCl ₂ aqueous solution was absorbed into 1 g of the same water absorbent resin used in Example 1. The resin-containing liquid thus obtained was used as the resin-containing liquid of Comparative Example 2.
(Comparative example 3)
Comparative Example 3 was prepared using 200 g of ion-exchanged water.
(Comparative example 4)
200 g of ion-exchanged water was absorbed into 1 g of the same water absorbent resin used in Example 1. The resin-containing liquid thus obtained was used as the resin-containing liquid of Comparative Example 4.

For Example 1 and Comparative Examples 1, 2, and 4, the sedimentation time in water, the sedimentation time in 0.05% CaCl ₂ aqueous solution, and the water absorption capacity were measured by the above-mentioned measurement method, and the results are shown in Table 1. In addition, the results of measuring (1) the ratio of the water-absorbing resin with low molecular weight using the following method, and the results of measuring (2) the viscosity of Example 1 and Comparative Examples 1 to 4 using the following method are also shown. Shown in 1. Since the ion-exchanged water of Comparative Example 3 did not contain a water-absorbing resin, (1) the ratio of the low-molecular-weight water-absorbing resin was set to 0.

(1) Method for measuring the ratio of water-absorbing resin that has become low molecular weight 20 g of the resin-containing liquids of Example 1 and Comparative Examples 1, 2, and 4 were taken out, and 1980 g of ion-exchanged water was added and stirred to dilute 100 times. A mesh with an opening of 500 μm was prepared in advance, and its mass was measured. Thereafter, the diluted resin-containing liquids of Example 1 and Comparative Examples 1, 2, and 4 were filtered through the mesh. After drying, the total mass of the mesh and the water-absorbing resin remaining on the mesh was measured. The value calculated by subtracting the mass of the mesh itself from the measured total mass was defined as the mass of the water-absorbing resin remaining on the mesh. The values calculated by subtracting the mass of the water-absorbing resin remaining in the mesh from the mass (0.1 g) of the water-absorbing resin contained in the resin-containing liquids of Example 1 and Comparative Examples 1, 2, and 4 before dilution, respectively. , divided by the mass (0.1 g) of the water-absorbing resin contained in the resin-containing liquids of Example 1 and Comparative Examples 1, 2, and 4 before dilution. The value obtained by multiplying the value calculated in this manner by 100 was defined as the proportion of the water-absorbing resin reduced in molecular weight in Example 1 and Comparative Examples 1, 2, and 4, respectively. The proportion of the water-absorbing resin that has been reduced to a low molecular weight is the proportion of the water-absorbing resin that has passed through the mesh.

(2) Viscosity measurement method The viscosity of the resin-containing liquids of Example 1 and Comparative Examples 1 to 4 was measured using a B-type viscometer (model number TVB-10M, manufactured by Toki Sangyo Co., Ltd.). In Example 1 and Comparative Examples 1 and 4, measurement conditions were as follows: Rotor No. 23 (M4), 30 rpm, 60 seconds, Comparative Examples 2 and 3 were measured under the following measurement conditions: Rotor No. 19 (M1), 30 rpm, and 60 seconds.

〔Test results〕
In Example 1, no precipitation occurred when 3600 seconds had elapsed from the end of stirring, even when the precipitation time was measured using either pure water or a 0.05% CaCl ₂ aqueous solution. "3600 or more" in Table 1 indicates that no precipitation occurred after 3600 seconds had passed from the end of stirring.
As shown in Table 1, in Example 1, the sedimentation time in pure water and 0.05% CaCl ₂ aqueous solution was 1 minute or more, and the water absorption capacity was 10 times or less. Therefore, it can be seen that Example 1 has a low molecular weight.
On the other hand, in Comparative Example 1, the sedimentation time in pure water and 0.05% CaCl ₂ aqueous solution was 1 minute or more, but the water absorption capacity was more than 10 times. Furthermore, in Comparative Example 2, the water absorption capacity is 10 times or less, but the sedimentation time in pure water and 0.05% CaCl ₂ aqueous solution is less than 1 minute. Furthermore, in Comparative Example 3, the sedimentation time in pure water and 0.05% CaCl ₂ aqueous solution was less than 1 minute, and the water absorption capacity was more than 10 times. Therefore, it can be seen that Comparative Examples 1, 2, and 4 were not reduced in molecular weight.

Furthermore, as shown in Table 1, in Example 1, the proportion of low-molecular water absorbent resin was 60%, whereas in Comparative Examples 1, 2, and 4, the proportion of low-molecular water absorbent resin was 60%. The percentage was 0%. As described above, since Example 1 has a higher proportion of low-molecular-weight water-absorbing resin than Comparative Examples 1, 2, and 4, the method of lower-molecular-weight water-absorbing resin of the present invention has a higher efficiency. It can be seen that the water-absorbing resin can be made to have a low molecular weight.
Further, as shown in Table 1, Example 1 has a higher viscosity than Comparative Examples 1 to 4. As described above, in Example 1, the water-absorbing resin becomes low-molecular and the molecular chains of the resin become easily entangled. It can be seen that it is possible to reduce the molecular weight. Furthermore, it can be seen that according to the method of reducing the molecular weight of a water-absorbing resin of the present invention, it is possible to increase the adhesive strength of paper and to produce a water-absorbing resin with high viscosity.

<Test 2>
Test 2 was conducted to evaluate the quality of recycled paper produced using a paper composition containing a water-absorbing resin of low molecular weight.
[Manufacture of recycled paper]
(Example 2)
0.25 g of the resin-containing liquid of Example 1 was dissolved in 475 g of a 0.5% pulp suspension, which was then papered and dried to produce recycled paper of Example 2.

(Comparative example 5)
In Example 2, recycled paper of Comparative Example 5 was produced in the same manner as in Example 2, except that the resin-containing liquid of Comparative Example 1 was used in place of the resin-containing liquid of Example 1.
(Comparative example 6)
In Example 2, recycled paper of Comparative Example 6 was produced in the same manner as in Example 2, except that the resin-containing liquid of Comparative Example 2 was used in place of the resin-containing liquid of Example 1.
(Comparative example 7)
In Example 2, recycled paper of Comparative Example 7 was produced in the same manner as in Example 2, except that ion-exchanged water of Comparative Example 3 was used in place of the resin-containing liquid of Example 1.

Table 2 shows the results of measuring the thickness, basis weight, number of holes, dry strength, wet strength, feel, thickness, ash content, and sodium content in ash for the recycled papers of Example 2 and Comparative Examples 5 to 7. Shown below.

[Measuring method of thickness]
Sample pieces for measurement with a length of 200 mm and a width of 100 mm were cut from the recycled papers of Example 2 and Comparative Examples 5 to 7. For each sample piece for measurement, the thickness at five arbitrary locations under a load of 25 kg/ ^m2 was measured using a laser displacement meter (manufactured by OMRON Corporation, model number: ZS-LDC), and the measured value was The average value was taken as the thickness of the recycled paper of Example 2 and Comparative Examples 5 to 7.

[Method of measuring basis weight]
Sample pieces for measurement with a length of 200 mm and a width of 100 mm were cut from the recycled papers of Example 2 and Comparative Examples 5 to 7. The mass of the sample piece for measurement was measured, and the value divided by the area was taken as the basis weight of the recycled paper of Example 2 and Comparative Examples 5 to 7, respectively.

[Method of measuring the number of holes]
Sample pieces for measurement with a length of 200 mm and a width of 100 mm were cut from the recycled papers of Example 2 and Comparative Examples 5 to 7. For each sample piece for measurement, the sample piece was placed on a black mount, and a fluorescent light was applied from vertically above, and an image was taken from vertically above using a digital camera (PowerShot S120, manufactured by Canon Inc.). . The photographed image was opened with image processing software (Adobe Photoshop CSS version 12.0, manufactured by Adobe) and binarized, and then the number of particles was measured using the same software. By placing a black mount underneath, the color of the pores becomes black, and the pores stand out due to binarization, making it easier to measure the number of particles. The smaller the number of pores, the better.

[Method of measuring dry strength]
Sample pieces for measurement with a length of 120 mm and a width of 25 mm in the MD direction were cut from the recycled papers of Example 2 and Comparative Examples 5 to 7. The strength of the measurement sample piece was measured using a tensile tester ("Tensilon" RTC-1150A, manufactured by Orientec Co., Ltd.). The distance between chucks was 100 mm, and the pulling speed was 300 mm/min. The maximum strength until the sample broke was measured five times, and the average was taken as the dry strength. The higher the dry strength, the better.

[Method of measuring wet strength]
The strength was measured in the same manner as described above [method for measuring dry strength], except that the strength was measured after tracing the center part of the sample piece for measurement in the CD direction with a brush moistened with water. By setting the amount of water attached to the sample to be 5 to 15 mg, a moderately moist state similar to that obtained when the entire sample is immersed can be achieved. Even if water is partially attached, the liquid spreads due to capillary action and naturally becomes a moderately moist state. Therefore, even if the amount of liquid is large in some areas, if the sample is attached across the measurement direction, No effect was observed on the measurement results. The value measured in this manner was defined as the wet strength. The higher the wet strength, the better.

[Feel evaluation method]
Sample pieces for measurement with a length of 200 mm and a width of 100 mm were cut from the recycled papers of Example 2 and Comparative Examples 5 to 7. The surface of each of the measurement sample pieces was traced with a finger at five arbitrary locations to evaluate the graininess caused by the water-absorbing resin. Feeling the graininess is when you feel a little pain when you compress it strongly with your fingers. The evaluation was based on two levels of sensory values: grainy and no grainy. It is preferable to have no graininess.
No graininess: I traced it in different places five times and did not feel any graininess at all.
Grainy feeling: Traced on different places five times and felt grainy at least once.

[Measurement method of ash content]
Approximately 5 mg was cut out from the recycled paper of Example 2 and Comparative Examples 5 to 7, weighed on a balance, placed in a φ5 open pan (aluminum), and heated using STA7200RV (trade name) manufactured by Hitachi High-Tech Science. Measurements were performed up to 500°C at a rate of 10°C/min. Thereafter, the ash remaining on the bread was deposited with gold, and then an elemental particle (EDS) analysis was performed using an energy dispersive X-ray analyzer (EDX) attached to a scanning electron microscope (SEM). In the EDX operation, the X-ray extraction angle was 30°, the X-ray folding time was 30 minutes, and a Si(Li) semiconductor detector was used for X-ray detection. Elements are calculated by counting the amount of X-rays unique to eight atoms: carbon: C, oxygen: O, sodium: Na, magnesium: Mg, aluminum: AL, silicon: Si, gold: Au, and calcium: Ca. The ratio of each element was measured by setting the total amount of X-rays as 100. This operation was repeated five times, the average elemental ratio was calculated, and the ash content was calculated using the following formula.
(Ash content) = (1 - (mass loss rate up to 500°C)) x (100 - (ash carbon: C ratio) - (ash gold: Au ratio)) / 100

[Method for measuring sodium content in ash]
Approximately 5 mg was cut out from the recycled paper of Example 2 and Comparative Examples 5 to 7, weighed on a balance, placed in a φ5 open pan (aluminum), and heated using STA7200RV (trade name) manufactured by Hitachi High-Tech Science. Measurements were performed up to 500°C at a rate of 10°C/min. Thereafter, the ash remaining on the bread was deposited with gold, and then an elemental particle (EDS) analysis was performed using an energy dispersive X-ray analyzer (EDX) attached to a scanning electron microscope (SEM). In the EDX operation, the X-ray extraction angle was 30°, the X-ray folding time was 30 minutes, and a Si(Li) semiconductor detector was used for X-ray detection. Elements are calculated by counting the amount of X-rays unique to eight atoms: carbon: C, oxygen: O, sodium: Na, magnesium: Mg, aluminum: AL, silicon: Si, gold: Au, and calcium: Ca. The ratio of each element was measured by setting the total amount of X-rays as 100. This operation was repeated five times, the average elemental ratio was calculated, and the sodium content in the ash was calculated using the following formula.
(Sodium content in ash) = (Sodium: Na ratio in ash) / (100 - (Carbon: C ratio in ash) - (Gold: Au ratio in ash))

〔Test results〕
As shown in Table 2, Example 2 and Comparative Examples 5 and 6, which contain a water-absorbing resin, have higher dry strength and wet strength than Comparative Example 7, which does not contain a water-absorbing resin. Therefore, it can be seen that recycled paper has higher strength by containing a water-absorbing resin. Furthermore, compared to Comparative Example 7, Example 2 and Comparative Examples 5 and 6 are thicker. Therefore, it can be seen that recycled paper becomes bulky due to the inclusion of water-absorbing resin.
Comparing Example 2 and Comparative Examples 5 and 6, the recycled paper of Comparative Examples 5 and 6 has many holes, whereas the recycled paper of Example 2 has no holes.
As is clear from the above description, the recycled paper of the present invention has high dry strength, high wet strength, and high bulk, and has no pores.

1 Absorbent article 2 Top sheet 3 Back sheet 4 Absorber 8 Sheet piece derived from absorbent article 9 Mass of absorbent material

Claims (12)

A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
A paper composition in which the water-absorbing resin has a low molecular weight. A paper composition comprising pulp recovered from an absorbent article and a water absorbent resin,
The water-absorbing resin is a paper composition that passes through a sieve with an opening of 1000 μm in a wet state in which 200 times the amount of water by mass is added. The paper composition according to claim 1 or 2, wherein the content of sodium in the ash is 15% or more. The paper composition according to any one of claims 1 to 3, having an ash content of 0.65% by mass or less. Recycled paper containing pulp and water absorbent resin recovered from absorbent articles,
Recycled paper in which the water-absorbing resin has a low molecular weight. The recycled paper according to claim 5, wherein 15% or more of the ash content is sodium. The recycled paper according to claim 6, having an ash content of 0.65% by mass or less. An absorbent comprising one or more selected from the group consisting of the paper composition according to any one of claims 1 to 4 and the recycled paper according to any one of claims 5 to 7. Sex items. A method for producing a paper composition comprising pulp recovered from an absorbent article and a water absorbent resin, the method comprising:
a freezing step of freezing the moisture in the absorbent article;
After the freezing step, a crushing step of applying an impact to the absorbent article to crush the absorbent article;
After the crushing step, a separation step of separating the absorbent material containing the pulp and the water-absorbing resin from the sheet piece derived from the absorbent article, and
A method for producing a paper composition, comprising, after the separation step, a low-molecularization step of reducing the molecular weight of the water-absorbing resin contained in the absorbent material. The molecular weight reduction step is as follows:
a hydrating step of adding water to the water-absorbing resin;
a resin freezing step of freezing the water absorbent resin;
The method for producing a paper composition according to claim 9, comprising a resin pulverizing step of pulverizing the water absorbent resin. A method of reducing the molecular weight of a water-absorbing resin,
a hydrating step of adding water to the water-absorbing resin;
a resin freezing step of freezing the water-absorbing resin after the hydration step;
A method for reducing the molecular weight of a water-absorbing resin, comprising, after the freezing step, a resin pulverizing step of pulverizing the water-absorbing resin. An apparatus for processing water-absorbing resin to lower molecular weight,
a water-containing part that contains water in the water-absorbing resin;
a resin freezing section that freezes the water absorbent resin;
A water absorbent resin low molecular weight processing apparatus, comprising a resin crushing section that crushes the water absorbent resin.

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